The latest contribution to the perennial discussion, suggesting:
QuoteWe generated genome-wide data from 69 Europeans who lived between 8,000–3,000 years ago by enriching ancient DNA libraries for a target set of almost 400,000 polymorphisms ... These results provide support for a steppe origin of at least some of the Indo-European languages of Europe.
http://www.nature.com/nature/journal/v522/n7555/full/nature14317.html
This bears on the same genetic-origin-of-the-Yamnaya-population point as the previous link:
"Europe's fourth ancestral 'tribe' uncovered" - http://www.bbc.co.uk/news/science-environment-34832781
"Upper Palaeolithic genomes reveal deep roots of modern Eurasians" - http://www.nature.com/ncomms/2015/151116/ncomms9912/full/ncomms9912.html
Confirming long held beliefs by many... Thanks for the posts Duncan!